Effectiveness of chitosan preparations against Brettanomyces bruxellensis grown in culture media and red wines

Abstract

<p style="text-align: justify;"><strong>Aim</strong>: The antimicrobial properties of chitosan from different sources (fungal, crab shell, and lactate-forms) against <em>Brettanomyces bruxellensis</em> in culture media and red wines were investigated.</p><p style="text-align: justify;"><strong>Methods and results</strong>: While concentrations of 4 to 8 g/hL were needed for crab shell or lactate-forms of chitosan to reduce yeast viability in liquid media, fungal chitosan did not exhibit antimicrobial activities no matter the concentration. <em>B. bruxellensis</em> E1 and I1a were inoculated into Cabernet Sauvignon wine at 10⁶ cfu/mL and treated with 0, 4, 8 and 12 g/hL fungal chitosan. In contrast to previous results with media, addition of fungal chitosan to a red wine resulted in a three-log reduction of culturability. Addition of fungal chitosan also reduced the viability of <em>B. bruxellensis</em> growing in oak barrels containing Merlot wine from 10⁵ cfu/mL down to ≈10² cfu/mL.</p><p style="text-align: justify;"><strong>Conclusion</strong>: Depending on concentration, all preparations of chitosan added to red wines greatly reduced populations of <em>B. bruxellensis</em>. However, wines were not completely stable after treatment as populations eventually increased.</p><p style="text-align: justify;"><strong>Significance and impact of the study</strong>: As <em>B. bruxellensis</em> is considered to be a worldwide threat to wine quality, it is crucial to improve knowledge of alternative control methods and strategies such as chitosan that winemakers can apply.</p>